I haven't played this variant but I am intending to do so tomorrow. One thought has crossed my mind though - following the logic of reducing the resources and development cards would it also be appropriate to reduce the total display of items to be auctioned to 7 in a round rather than keeping it at 9? I suggest a minimum of 2 tiles and 2 development cards. This would mean 12 rounds compared to 13 in the normal 4 game. Keeping the display at 9 would reduce the rounds to 9 which seems to mitigate against the intention of keeping the board tight.
This is a fine idea, John, and it is a logical extension of the the other resource reductions I've proposed.